Biology and Environment Affect Childhood Behavioral Development

They’re the kids who every parent loves to hate. The childhood delinquents. The ones whom you hope your kids never start hanging out with, much less become. For whatever reason, they fell through the cracks and and seem destined for tribulation. They do poorly in school, get into fights, shirk the rules, and end up on the wrong side of the law. They “live fast and die young.”

Their problems have generally been attributed to disposition — theirs or their parents. Perhaps the nogoodnicks have learning disorders or, were never properly disciplined, or more likely, are just bad apples.

A recent study by Daniel Hart at Rutgers Universitysuggests a more situational cause: stress response. By measuring neurological responses to external stimuli, Prof. Hart was able to find a spectrum of responses to these stresses placed on youths. Amy Norton of Reuters reports.

A combination of nature and nurture may make some children more likely to develop behavioral problems, new research suggests.

In a study of 138 children, researchers found that it wasn’t only the children’s exposure to stress, but their bodies’ reactions to the stress, that affected their future behavior.

Young children who had both a stressful home life and an exaggerated nervous system response to stress were more likely than their peers to develop behavioral problems over the next six years.

The findings suggest that family life and biology combine to shape a child’s personality development, the researchers report in the journal Psychological Sciences.

In the case of children who are surrounded by stressful conditions and have a stronger physiological response to stress, the combination may set them on a course toward an “under controlled” personality, according to the study.

Young people with this personality type have difficulty adapting their behavior to different circumstances, tend to be plagued by negative emotions, and often have behavioral problems such as fighting with their peers.

The findings suggest that children with greater nervous system reactivity have a particular need to be shielded from chronic stress, lead study author Daniel Hart told Reuters Health.

“What some kids can shrug off (may) be harmful to others,” explained Hart, a psychologist at the Center for Children and Childhood Studies at Rutgers University in Camden, New Jersey.

He and his colleagues based their findings on a six-year follow-up of 138 children who were in kindergarten through third grade at the study’s start. At that time, the researchers measured the children’s autonomic nervous response to stress.

The autonomic nervous system regulates involuntary bodily functions like heart rate and digestion. Hart’s team gauged the children’s autonomic responses to stress using a test that measures sweat production on the palms. The children were tested after seeing a short, emotionally neutral film, and after seeing a more stressful scene where a lamp triggers a fire in a girl’s room.

The researchers also estimated the children’s risk of having a stressful home life based on family income and mothers’ education; children from low-income, less educated families were considered to be at risk of living under stressful conditions.

In general, the study found, children who had both a high risk of family stress and exaggerated responses to the stressful film were more likely to develop behavioral problems over the next six years.

But while the findings suggest that nature is important in a child’s personality development and likelihood of behavior problems, nurture may win in the end.

In their ongoing research, Hart said, he and his colleagues have found that when children who are prone to greater stress reactions do not have chronic stress in their lives, they “may really flourish.”

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Understanding how interior and exterior situation (nature and nurture) influence development will help create an environment where fewer kids will ‘slip through the cracks’. If you are interested in reading Prof. Hart’s study, his paper is available for purchase here.